This invention relates to an insulated gate bipolar transistor.
It is known in the art that insulated gate bipolar transistors (IGBTs) have a limited life, and that one of the factors that influence the lifespan of an IGBT is the change in temperature seen by the junction as a result of flash heat. When an IGBT switches from its OFF state to its ON state and allows current to flow from its collector to its emitter, a flash of heat (referred to as “flash heat”) is created. In current IGBTs the flash heat is initially isolated to the top metal layer of the IGBT, and, over time, is diffused through the junction into the base and ultimately diffuses into a silicone layer of the IGBT where it is then dissipated into the surrounding air. Diffusion through the silicon layer takes a relatively long time, and as such the temperature of the IGBT junction is raised significantly above its ambient temperature before the flash heat is fully dissipated.
The present construction methods for IGBTs utilize wire bound connectors to electrically connect the IGBT emitter to the electrical system. The wire bound connections have a high thermal resistance and constructions using this technique can only efficiently dissipate heat through the ceramic side of the IGBT into the silicone layer as the wirebound connections prevent efficient heat dissipation through the electrical connection side. Since the wirebound connections prevent the heat from being dissipated except through the silicone layer, little can be done in current designs to reduce the temperature change as a result of flash heat and therefore, the lifespan of current designs is limited.